1. Technical Field
The present invention relates to a liquid ejecting apparatus such as an ink jet type recording apparatus, a control method of a liquid ejecting head mounted in the liquid ejecting apparatus, and a control method of the liquid ejecting apparatus. Particularly, the invention relates to a liquid ejecting apparatus a control method of the liquid ejecting head and a control method of the liquid ejecting apparatus that perform a maintenance process in which a liquid is ejected from nozzles and ejection performance of the liquid ejecting head is restored.
2. Related Art
A liquid ejecting apparatus includes a liquid ejecting head to eject (discharge) various types of liquid from the liquid ejecting head. The liquid ejecting apparatus includes, for example, an ink jet type printer, an ink jet type plotter and the like. Recently, however, in order to use an advantage that an extreme small amount of liquid can be exactly landed on a predetermined position, the liquid ejecting apparatus is also applied to various types of manufacturing apparatuses. For example, the liquid ejecting apparatus is applied to a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming electrodes such as organic electro luminescence (EL) display, FED (a surface light emitting display) and the like, and a chip manufacturing apparatus for manufacturing a biochip (biochemical element). Further, a recording head for an image recording apparatus ejects a liquid ink, whereas a coloring material ejecting head for a display manufacturing apparatus ejects solution of each coloring material such as red (R), green (G), or blue (B). Further, an electrode material ejecting head for an electrode forming apparatus ejects a liquid electrode material, and a bio-organic material ejecting head for a chip manufacturing apparatus ejects a solution of the bio-organic material.
In a liquid ejecting head, air bubbles are likely to be mixed into the liquid in the nozzle. Specifically, for example, when a wiping member (such as a wiper formed of an elastic member) slides on a surface on which nozzles of the liquid ejecting head are formed to wipe and clean the nozzle surface, the air bubbles are likely to penetrate into the liquid in the nozzle. Further, a very fine paper powder is likely to be generated from the recording paper as a recording media, and likely to be attached to the nozzle surface and enter into the nozzle, and thereby the air bubbles enter into the liquid in the nozzle through the entered paper powder. Furthermore, when the liquid thickened in the vicinity of the nozzle is ejected, the air bubbles are also likely to enter into the liquid.
In the liquid ejecting apparatus with such a type of liquid ejecting head mounted thereon, in order to discharge the air bubbles or the thickened liquid in the nozzle or in the pressure chamber of the liquid ejecting head, a maintenance process so called flushing is performed in which the liquid is forced to be ejected from the nozzle (see, for example, JP-A-2009-073076), independently of the liquid ejecting process for an landing target such as the recording media, that is, the ejecting process for original purpose. In the flushing process, a drive waveform is applied to an actuator to drive the actuator to cause a pressure variation of the liquid in the pressure chamber communicating with the nozzle, and thereby the pressure variation is used to eject (also referred to as releasing strike or idle discharge) the liquid from the nozzle. In this case, generally, after the pressure chamber is firstly decompressed to attract a meniscus in the nozzle to the pressure chamber, the pressure is drastically compressed to extrude the meniscus to a side (an ejection side) opposite to the pressure chamber and thereby the liquid droplet is ejected from the nozzle. Such an operation is continuously repeated a predetermined number of times to discharge the thickened liquid in the nozzle or the pressure chamber.
However, in the flushing process of the related art, it is difficult to discharge the air bubbles inside the liquid in the nozzle. Specifically, during the first-time decompression in the pressure chamber in the flushing process of the related art, the air bubbles moves to the pressure chamber and thus air bubbles are hardly discharged even though the flushing process is repeatedly performed.